1. Technical Field
The present technology relates to a pneumatic tire by which driving performance, braking performance, and turning performance on snowy and icy roads are enhanced to or beyond conventional levels.
2. Related Art
Superior driving performance, braking performance, and turning performance or similar steering stability when traveling on snowy and icy roads is necessary for studless tires such as winter tires and all-season tires used for traveling on snowy and icy roads. Conventionally, as illustrated in FIGS. 11 and 12, a land portion 3 formed from a block or a rib partitioned by circumferential grooves 1 and lateral grooves 2 including lug grooves is provided in a tread portion. A plurality of sipes 15 and 16 are formed in this land portion 3 thereby increasing pliability of the land portion and increasing actual ground contact area. Moreover, steering stability on snow (performance on snow) is ensured due to the biting action by the edges of the sipes 15 and 16. This performance on snow can be enhanced by increasing the snow traction component by adjusting the length, number, and the like of the sipes 15 and 16. However, with such conventional sipes, while high traction in the tire circumferential direction can be obtained, traction in the tire width direction declines and steering stability on snow and ice when turning cannot be sufficiently obtained.
In response, Japanese Unexamined Patent Application Publication No. 2006-347468A and Japanese Unexamined Patent Application Publication No. 2010-274800A propose, as illustrated in FIGS. 13 and 14, disposing a sipe that is a combination of a round annular sipe 17 and a cross-shaped sipe 18, and a honeycomb shaped sipe 19 having collectively arranged hexagonal annular sipes. Compared to the conventional sipes 15 and 16, the sipes described in Japanese Unexamined Patent Application Publication No. 2006-347468A or Japanese Unexamined Patent Application Publication No. 2010-274800A function to enhance driving performance, braking performance, turning performance and similar steering stability when traveling on snowy and icy roads. However, these improvement effects are not always sufficient and further enhancements in performance on snow and ice is needed.